Cannula assembly

ABSTRACT

Cannula assemblies and methods of manufacturing cannula assemblies are provided. The cannula assembly includes a cannula and a pigtail extension coupled to the cannula. The pigtail extension includes a proximal section having a first stiffness and a distal section having a second stiffness, the first stiffness greater than the second stiffness. The proximal section of the pigtail extension is positioned between the cannula and at least a portion of the distal section.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119(e)from U.S. Provisional Application Ser. No. 61/992,825 filed May 13,2014, the content of which is hereby incorporated herein by reference inits entirety.

TECHNICAL FIELD

The present disclosure relates to cannula assemblies. More specifically,the present disclosure relates to cannula assemblies implementable witha blood pump assembly, such as an intravascular heart pump system.

BACKGROUND

Blood pump assemblies, such as intracardiac or intravascular blood pumpsmay be introduced in the heart to deliver blood from the heart into anartery. Blood pump assemblies may be introduced percutaneously during acardiac procedure through the vascular system. Specifically, blood pumpassemblies can be inserted via a catheterization procedure through thefemoral artery or the axillary/subclavian artery, into the ascendingaorta, across the valve and into the left ventricle. The inserted bloodpump assembly pulls blood from the left ventricle of the heart through acannula and expels the blood into the aorta.

The stability of a blood pump assembly in the ventricle impacts the useand performance of the pump. Positioning a blood pump assembly too closeto the ventricle apex can lead to suction and arrhythmia problems.Positioning a blood pump assembly too deep in the ventricle can resultin the outlet being on the aortic valve or in the ventricle.Mispositioning the blood pump assembly causes consumption of valuabletime as the blood pump assembly is repositioned. The time consumedrepositioning the blood pump assembly may be vital as proceduresrequiring such an implementation impact the sustainability and qualityof the life of a patient.

SUMMARY

The systems, methods, and devices disclosed herein provide a cannulaassembly for an intravascular blood pump. The cannula assembly includesa cannula coupled to a dual stiffness pigtail extension. The dualstiffness pigtail extension has a relatively stiff proximal section anda relatively soft distal section. The intravascular blood pump mayproduce thrust forces that compress the cannula assembly against apatient's tissue. The stiff proximal section is stiff enough tosubstantially resist buckling under such compression (e.g., a hardnessof 60, 70, 80, 90, 100 or higher on the Shore D scale). In contrast, thedistal portion may be soft and flexible enough so that it does tend tobuckle against the patient's tissue (e.g., a hardness of 50, 40, 30, 20or lower on the Shore D scale). This controlled buckling allows theproximal region of the pigtail extension to substantially maintain itsoriginal length so that it can act as a mechanical spacer. This spacingcan facilitate the proper positioning of the intravascular blood pumprelative to the patient's heart or vasculature. For example, the stiffproximal section may prevent a blood inlet from being too close to aventricular wall to avoid suctioning tissue. Furthermore, the stiffproximal section may ensure that an outlet of the blood pump ispositioned on the opposite side of a valve (e.g., the aortic valve)relative to the inlet. This allows blood to be pumped out of theventricle to increase cardiac output. At the same time, the relativelysoft distal section may reduce trauma to a patient's tissue. Forexample, the softer material of the distal section may reduce stresslocally induced in the patient's tissue. Furthermore, the deformation ofthe distal section of the pigtail may increase the area over which anyforce transmitted to the tissue is distributed. As used herein,intravascular refers to a component that is positioned, in whole or inpart, in a patient's vasculature, within a patient's heart, or withinboth. Furthermore, as used herein, dual stiffness refers to a componenthaving at least two sections of differing stiffness.

In some implementations, a kit is provided including a cannula and twoor more pigtail extensions having relatively stiff proximal sections ofvarying lengths (e.g., 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm or anyother suitable length). Each pigtail extension in the kit has a proximalend portion configured to couple to a distal end portion of the cannula.The coupling may be detachable to allow the physician to change apigtail extension that is originally coupled to the cannula assembly.This allows a physician to select a pigtail extension that provides theproper spacing for positioning the intravascular blood pump for aparticular patient. In some implementations, the appropriate length ofthe stiff proximal section is determined using imaging (e.g., X-ray,MRI, CT scan, fluoroscopy, or ultrasound) or estimated using patientdata (e.g., height, sex, age, or weight).

Various implementations provide blood pump assemblies and methods ofmanufacturing and implementing blood pump assemblies. Variousimplementations provide a cannula assembly including a cannula and apigtail extension coupled to the cannula. The pigtail extension includesa proximal section having a first stiffness and a distal section havinga second stiffness, the first stiffness greater than the secondstiffness. The proximal section of the pigtail extension is positionedbetween the cannula and at least a portion of the distal section.

In particular implementations, the cannula assembly includes a pumpcoupled to the cannula. The cannula is positioned between the pump andthe pigtail extension. The cannula assembly may include an impellerblade rotatably coupled to the pump motor. The impeller blade ispositioned at least in part in the pump housing component, in accordancewith particular implementations. The pump is coupled to the cannula by apump housing component including a plurality of blood exhaust apertures,in accordance with particular implementations. In particularimplementations, the pump housing component includes a peripheral wallextending about a rotation axis of the impeller blade. The peripheralwall includes a plurality of blood exhaust apertures; each blood exhaustaperture in the plurality of blood exhaust apertures is encircled by acircumferential aperture edge. The circumferential aperture edge extendsacross the peripheral wall from an inner peripheral wall surface to anouter peripheral wall surface. The circumferential aperture edgeincludes a rounded edge portion, rounded between the inner peripheralwall surface and the outer peripheral wall surface, in accordance withparticular implementations. The cannula component may include a bloodinlet manifold. The blood inlet manifold may include a plurality ofinlet openings. In particular implementations, the proximal section ofthe pigtail extension is composed of nylon. In particularimplementations, the proximal section of the pigtail extension iscomposed of a polymer including, but not limited, to one or more ofpolyurethane or pebax. In particular implementations, the distal sectionof the pigtail extension is composed of pebax. In particularimplementations, the distal section of the pigtail extension is composedof a polymer including, but not limited to, polyurethane. The proximalsection of the pigtail extension may have a hardness or durometer in therange of 60-100 Shore D. The distal section of the pigtail extension mayhave a hardness or durometer in the range of 20-50 Shore D. Thestiffness of the proximal portion may be altered by the addition ofother materials such as glass filler or metal or fiber braids.

Various implementations provide a method of manufacturing a cannulaassembly. The method includes coupling a pigtail extension to a cannula.The pigtail extension includes a proximal section having a firststiffness and a distal section having a second stiffness that is lessthan the first stiffness. The proximal section is positioned between thecannula and at least a portion of the distal section. The method alsoincludes coupling a pump to the cannula. The cannula is positionedbetween the pump and the pigtail extension.

In particular implementations, an impeller blade is rotatably coupled tothe pump motor. The impeller blade is positioned at least in part in thepump housing component, in accordance with particular implementations.The pump is coupled to the cannula by a pump housing component includinga plurality of blood exhaust apertures, in accordance with particularimplementations. The pigtail extension may be coupled to the cannula viaa blood inlet manifold. The blood inlet manifold may include a pluralityof inlet openings. In particular implementations, the proximal sectionof the pigtail extension is composed of nylon. In particularimplementations, the proximal section of the pigtail extension iscomposed of a polymer including, but not limited to, one or more ofpolyurethane or pebax. In particular implementations, the distal sectionof the pigtail extension is composed of pebax. In particularimplementations, the distal section of the pigtail extension is composedof a polymer including, but not limited to, polyurethane.

Variations and modifications will occur to those of skill in the artafter reviewing this disclosure. The disclosed features may beimplemented, in any combination and subcombination (including multipledependent combinations and subcombinations), with one or more otherfeatures described herein. The various features described or illustratedabove, including any components thereof may be combined or integrated inother systems. Moreover, certain features may be omitted or notimplemented. It should be appreciated that all combinations of theforegoing concepts and additional concepts discussed in greater detailbelow (provided such concepts are not mutually inconsistent) arecontemplated as being part of the inventive subject matter disclosedherein. In particular, all combinations of claimed subject matterappearing at the end of this disclosure are contemplated as being partof the inventive subject matter disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled artisan will understand that the drawings primarily are forillustrative purposes and are not intended to limit the scope of thesubject matter described herein. The drawings are not necessarily toscale; in some instances, various aspects of the subject matterdisclosed herein may be shown exaggerated or enlarged in the drawings tofacilitate an understanding of different features. In the drawings, likereference characters generally refer to like features (e.g.,functionally similar and/or structurally similar elements).

FIG. 1 shows a view of a cannula assembly, in accordance with exampleimplementations.

FIG. 2 shows a sectional side view of a pigtail extension, in accordancewith example implementations.

FIG. 3 shows an end view of the pigtail extension of FIG. 2.

FIG. 4 depicts a method of manufacturing a cannula assembly, accordingto certain implementations.

The features and advantages of the inventive concepts disclosed hereinwill become more apparent from the detailed description set forth belowwhen taken in conjunction with the drawings.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various conceptsrelated to, and implementations of, inventive systems and methods ofproviding a cannula assembly. It should be appreciated that variousconcepts introduced above and discussed in greater detail below may beimplemented in any of numerous ways, as the disclosed concepts are notlimited to any particular manner of implementation. Examples of specificimplementations and applications are provided primarily for illustrativepurposes.

The systems, methods, and devices disclosed herein provide a cannulaassembly for an intravascular blood pump. The cannula assembly includesa cannula coupled to a dual stiffness pigtail extension. The dualstiffness pigtail extension has a relatively stiff proximal section anda relatively soft distal section. The intravascular blood pump mayproduce thrust forces that compress the cannula assembly against apatient's tissue. The stiff proximal section is stiff enough tosubstantially resist buckling under such compression (e.g., a hardnessof 60, 70, 80, 90, 100 or higher on the Shore D scale). In contrast, thedistal portion may be soft and flexible enough so that it does tend tobuckle against the patient's tissue (e.g., a hardness of 50, 40, 30, 20or lower on the Shore D scale). This controlled buckling allows theproximal region of the pigtail extension to substantially maintain itsoriginal length so that it can act as a mechanical spacer. This spacingcan facilitate the proper positioning of the intravascular blood pumprelative to the patient's heart or vasculature. For example, the stiffproximal section may prevent a blood inlet from being too close to aventricular wall to avoid suctioning tissue. Furthermore, the stiffproximal section may ensure that an outlet of the blood pump ispositioned on the opposite side of a valve (e.g., the aortic valve)relative to the inlet. This allows blood to be pumped out of theventricle to increase cardiac output. At the same time, the relativelysoft distal section may reduce trauma to a patient's tissue. Forexample, the softer material of the distal section may reduce stresslocally induced in the patient's tissue. Furthermore, the deformation ofthe distal section of the pigtail may increase the area over which anyforce transmitted to the tissue is distributed. As used herein,intravascular refers to a component that is positioned, in whole or inpart, in a patient's vasculature, within a patient's heart, or withinboth. Furthermore, as used herein, dual stiffness refers to a componenthaving at least two sections of differing stiffness.

FIG. 1 shows a view of a blood pump assembly, in accordance with exampleimplementations. The blood pump assembly 100 includes a blood pump 101,a housing component 102, an impeller blade 103 rotatably coupled to theblood pump 101, a cannula 104, a blood inlet manifold 105, a pigtailextension 106, and a catheter 107. The blood pump 101 is coupled to thecannula 104 by the housing component 102 at a distal end of the cannula104. The blood pump 101 is also coupled to the catheter 107. In someimplementations, the blood pump 101 includes a motor. In such cases, thecatheter 107 may house electrical lines communicably coupling the pump101 to one or more electrical controllers or other sensors. In certainimplementations, the pump 101 is driven by a flexible shaft. In suchcases, the drive portion of the motor may be located outside of thepatient's body, and the catheter 107 may house the flexible shaft. Thecatheter 107 may also house other components, such as a purge fluidconduit, or other conduits configured to receive a guidewire or otherprocedure related components. The housing component 102 includes one ormore apertures or openings 109 configured to expel or exhaust blooddrawn into the cannula 104 out of the blood pump assembly 100. Inparticular implementations, the housing component 102 encapsulates theblood pump 101.

In particular implementations, the blood pump 101 includes a micro-axialpump having a pumping capability including, but not limited to, a rangeof 5 L/min to 2.5 L/min. In particular implementations, the blood pump101 includes a micro axial pump having a diameter including, but notlimited to, a range of 21 Fr to 10 Fr.

The cannula 104 may include an elongated flexible hose portion and mayinclude a shape memory coil, such as a nitinol coil. In particularimplementations, the cannula 104 is composed, at least in part, of apolyurethane material. In particular implementations, the cannula 104has a diameter including, but not limited to, a range of 12 Fr to 9 Fr.In particular implementations, the cannula 104 includes a 45° bend. Thecannula 104 includes the blood inlet manifold 105 coupled to the cannula104 at a proximal end of the cannula 104 to receive blood flow into theblood pump assembly 100. The blood inlet manifold 105 includes one ormore blood inlet openings positioned in the inlet manifold 105. Theblood inlet manifold 105 couples the pigtail extension 106 to thecannula 104.

The pigtail extension 106 assists with stabilizing and positioning theblood pump assembly 100 in the correct position in the left ventricle ofa heart. In particular implementations, the pigtail extension has anouter diameter including, but not limited to, a range of 4 Fr-8 Fr. Inimplementation, the blood pump assembly 100 is inserted percutaneouslythrough the femoral artery or the axillary/subclavian artery and intothe left ventricle. When properly positioned, the blood pump assembly100 delivers blood from the inlet area at the blood inlet manifold 105,which sits inside the left ventricle, through the cannula 104, to theoutlet openings of the housing component 102 positioned in the ascendingaorta.

In accordance with particular implementations, the pigtail extension 106is configurable from a straight configuration to a partially curvedconfiguration. FIG. 1 shows the pigtail extension in the curvedconfiguration. The curve is about an axis substantially orthogonal tothe central axis of the cannula. In some implementations the curve isgreater than 180 degrees (e.g., 200, 220, 240, 260, 270, 300, 320degrees, or any suitable angle). In some implementations the curve isless than 180 degrees (e.g., 90, 100, 120, 140, 160 degrees or anysuitable angle). Accordingly, the pigtail extension 106 may be composed,at least in part, of a flexible material. The pigtail extension 106 hasa dual stiffness. In particular, the pigtail extension 106 includes adistal section 107 and a proximal section 108, wherein the proximalsection 108 is composed of a material having a higher stiffness than thedistal section 107. The proximal section 108 may be composed of adifferent material and may have a different structure than the bloodinlet manifold 105 and the cannula 104. In certain implementations, theproximal section 108 is stiff enough to substantially prevent section108 from buckling, thereby spacing the blood inlet openings in the bloodinlet manifold 105 away from the ventricle apex of the heart. Thestiffness of proximal section 108 also reduces the probability of theblood outlet openings or blood exhaust apertures 109 in the housingcomponent 102 moving into the aortic valve of the heart or into theventricle of the heart. The distal section 107 of the pigtail extension106 is flexible compared to the proximal section 108 to provide anatraumatic tip for contact with the ventricle wall. The flexibility alsoallows a guidewire to be inserted through an inner conduit 210 of thepigtail extension 106. In particular implementations, the proximalsection 108 and the distal section 107 of the pigtail extension arecomposed of different materials having different stiffness. In certainimplementations, the proximal section 108 and the distal section 107 ofthe pigtail extension are composed of the same material having differentstiffness.

In some implementations, the length of the proximal section 108 of thepigtail extension is selected based on the size of a left ventricle of aspecific patient. For example, a physician may be provided with a kitincluding two or more pigtail extensions having stiff proximal sectionsof varying lengths. Each pigtail extension in the kit may have aproximal end portion that is configured to couple to the cannula (e.g.,at the blood inlet manifold 105). In particular, the proximal endportion of the pigtail extension may be configured for detachablecoupling to the cannula. For example, the proximal end portion of thepigtail extension may include a snap connection, an interference fit, ascrew type connector, or any other suitable reversible or detachableconnector. This allows the physician to change the pigtail extensionoriginally coupled to the cannula, while the connection to the pigtailextension is also secure enough to prevent disconnection within thepatient's vasculature. In certain implementations, this allows the kitto initially include a cannula having a “standard” sized pigtailinitially coupled to the catheter 104 that can be exchanged for a largeror smaller pigtail size as needed. The “standard” pigtail extension canbe sized to accommodate a significant portion of patients (e.g., 30%,40%, 50%, 60%, 70%, 80%, 90%, or 95%), while the larger or smaller sizesmay accommodate the remainder of patients. The physician may select thepigtail extension having a proximal section of the appropriate lengthbased on medical imaging. For example, the physician may use MRI, CT,X-ray, ultrasound, fluoroscopy or any other suitable imaging technique,to determine ventricle size. In certain implementations this size isdetermined pre-operatively. In some implementations, the physicianestimates the ventricle size using patient data (e.g., age, height,weight, sex).

FIG. 2 shows a sectional side view of a pigtail extension 206, inaccordance with example implementations. FIG. 3 shows an end view of thepigtail extension 206 of FIG. 2. The pigtail extension 206 includes aproximal section 208, a distal section 207 including a curved tip 212,and a conduit 210 for use with a guidewire. The pigtail extension 206has a dual stiffness because the proximal section 208 has a greaterstiffness than the distal section 207. In example implementations, thedistal section 207 and the proximal section 208 are composed of one ormore layers of materials provided to give the two sections differentstiffness. In certain implementations, the proximal section and thedistal section have a corresponding diameter. For example, the proximalsection 208 may be composed of a single layer of a first material havinga first thickness and a first stiffness, and the distal section 207 maybe composed of two layers of material. In such cases, the two layers mayinclude a first layer of the first material at a second thickness lessthan the first thickness and a second layer of a second material at athird thickness (the second and third thickness in aggregatecorresponding to the first thickness) and at a second stiffness.Accordingly, the distal section 207 has an overall lower stiffness thanthe proximal section 208 and may specifically be configured to curl orbuckle. The stiff proximal section 208 is stiff enough to substantiallyresist buckling under such compression (e.g., a hardness of 60, 70, 80,90, 100 or higher on the Shore D scale). The distal portion 207 is softand flexible enough so that it does tend to buckle against the patient'stissue (e.g., a hardness of 50, 40, 30, 20 or lower on the Shore Dscale).

In some implementations the proximal section may be of greater stiffnessthan the distal section due to the incorporation of additionalmaterials, such as metals, fibers, braided metal or fiber, glass or anyother suitable material, into the proximal section. The additionalmaterials may be added by injection molding, coextrusion, bonding, athermal reflow process, or any other suitable process. In someimplementations the additional materials form a matrix or other suitablestructure within the proximal section. The additional material mayextend from the proximal section partially into the distal section toreinforce the transition from the proximal section to the distalsection. In particular implementations, the additional materials may bedeposited between a first material layer and a second material layer ofthe stiff proximal section. Incorporation of additional materials intothe proximal section allows a difference in stiffness to be achievedusing a single base material between the proximal and distal sections.The use of a single base material between the proximal and distalsections may help achieve melting in the transition region between theproximal section and the distal section. This may facilitate the joiningof the proximal section to the distal section during manufacture.

The intravascular or intracardiac blood pump may produce thrust forcesthat compress the cannula assembly against a patient's tissue, and thestiffness of the proximal portion allows the proximal region to maintainits original length and act as a mechanical spacer to maintain properpositioning of the blood intravascular pump. Thus, the stiff proximalportion 208 may prevent a blood inlet from being too close to aventricular wall to avoid suctioning tissue. The stiff distal portion208 may ensure that an outlet of the blood pump (e.g., blood pump 101)is positioned on the opposite side of a valve (e.g., the aortic valve)relative to the inlet. This allows blood to be pumped out of theventricle to increase cardiac output. At the same time, the relativelysoft distal region may reduce trauma to a patient's tissue. For example,the softer material of the distal section may reduce stress locallyinduced in the patient's tissue. Furthermore, the deformation of thedistal section of the pigtail may increase the area over which any forcetransmitted to the tissue is distributed.

In particular implementations, the pigtail extension 206 includes acurved tip 212. In some implementations the pigtail extension 206 isconfigurable from a straight configuration to a partially curvedconfiguration. The curve of the curved tip is about an axissubstantially orthogonal to the central axis of the cannula. In someimplementations the curve is greater than 180 degrees (e.g. 200, 220,240, 260, 270, 300, 320 degrees, or any suitable angle). In particularimplementations the curve is less than 180 degrees (e.g., 90, 100, 120,140, 160 degrees or any suitable angle).

The pigtail extension 206 also includes the conduit 210 extendingthrough the proximal section and the distal section. The conduit 210 issized to receive a guidewire through the pigtail extension 206. Inparticular implementations, the proximal section 208 of the pigtailextension 206 is composed of nylon. In some implementations, theproximal section 208 of the pigtail extension 206 is composed of apolymer including, but not limited to, one or more of polyurethane orpebax. In particular implementations, the distal section 207 of thepigtail extension 206 is composed of pebax. In certain implementations,the distal section 207 of the pigtail extension 208 is composed of apolymer including, but not limited to, polyurethane. The proximalsection 208 of the pigtail extension 206 may have a hardness ordurometer in the range of 60-100 Shore D. The distal section 207 of thepigtail extension 208 may have a hardness or durometer in the range of20-50 Shore D. In accordance with particular implementations, the distalsection 207 of the pigtail extension 206 includes 25-75% of the totallength of the pigtail extension 206.

FIG. 4 depicts a method 400 for the manufacture of a cannula assemblyaccording to certain implementations. The method 400 may be implementedto manufacture the cannula assembly 100 in any of the aforementionedimplementations. In step 402, a dual stiffness pigtail extension, suchas the pigtail extensions 106 or 206 of FIGS. 1 and 2, is coupled to thecannula. The pigtail extension includes a relatively stiff proximalsection and a relatively flexible distal section. The pigtail extensionmay be detachably coupled to the cannula or the pigtail extension may bepermanently coupled to the cannula. In step 404, a pump is coupled tothe cannula such that the cannula is positioned between the pump and thepigtail extension.

As utilized herein, the terms “approximately,” “about,” “substantially”and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed without restricting the scope of these features to the precisenumerical ranges provided. Accordingly, these terms should beinterpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and areconsidered to be within the scope of the disclosure.

For the purpose of this disclosure, the term “coupled” means the joiningof two members directly or indirectly to one another. Such joining maybe stationary or moveable in nature. Such joining may be achieved withthe two members or the two members and any additional intermediatemembers being integrally formed as a single unitary body with oneanother or with the two members or the two members and any additionalintermediate members being attached to one another. Such joining may bepermanent in nature or may be removable or releasable in nature.

It should be noted that the orientation of various elements may differaccording to other exemplary implementations, and that such variationsare intended to be encompassed by the present disclosure. It isrecognized that features of the disclosed implementations can beincorporated into other disclosed implementations.

It is important to note that the constructions and arrangements ofapparatuses or the components thereof as shown in the various exemplaryimplementations are illustrative only. Although only a fewimplementations have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter disclosed. For example,elements shown as integrally formed may be constructed of multiple partsor elements, the position of elements may be reversed or otherwisevaried, and the nature or number of discrete elements or positions maybe altered or varied. The order or sequence of any process or methodsteps may be varied or re-sequenced according to alternativeimplementations. Other substitutions, modifications, changes andomissions may also be made in the design, operating conditions andarrangement of the various exemplary implementations without departingfrom the scope of the present disclosure.

While various inventive implementations have been described andillustrated herein, those of ordinary skill in the art will readilyenvision a variety of other mechanisms and/or structures for performingthe function and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the inventiveimplementations described herein. More generally, those skilled in theart will readily appreciate that, unless otherwise noted, anyparameters, dimensions, materials, and configurations described hereinare meant to be exemplary and that the actual parameters, dimensions,materials, and/or configurations will depend upon the specificapplication or applications for which the inventive teachings is/areused. Those skilled in the art will recognize, or be able to ascertainusing no more than routine experimentation, many equivalents to thespecific inventive implementations described herein. It is, therefore,to be understood that the foregoing implementations are presented by wayof example only and that, within the scope of the appended claims andequivalents thereto, inventive implementations may be practicedotherwise than as specifically described and claimed. Inventiveimplementations of the present disclosure are directed to eachindividual feature, system, article, material, kit, and/or methoddescribed herein. In addition, any combination of two or more suchfeatures, systems, articles, materials, kits, and/or methods, if suchfeatures, systems, articles, materials, kits, and/or methods are notmutually inconsistent, is included within the inventive scope of thepresent disclosure.

Also, the technology described herein may be implemented as a method, ofwhich at least one example has been provided. The acts performed as partof the method may be ordered in any suitable way unless otherwisespecifically noted. Accordingly, implementations may be constructed inwhich acts are performed in an order different than illustrated, whichmay include performing some acts simultaneously, even though shown assequential acts in illustrative implementations.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.” As used herein inthe specification and in the claims, “or” should be understood to havethe same meaning as “and/or” as defined above. For example, whenseparating items in a list, “or” or “and/or” shall be interpreted asbeing inclusive, i.e., the inclusion of at least one, but also includingmore than one, of a number or list of elements, and, optionally,additional unlisted items. Only terms clearly indicated to the contrary,such as “only one of” or “exactly one of” will refer to the inclusion ofexactly one element of a number or list of elements. In general, theterm “or” as used herein shall only be interpreted as indicatingexclusive alternatives (i.e., “one or the other but not both”) whenpreceded by terms of exclusivity, such as “either,” “one of,” “only oneof,” or “exactly one of.”

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one implementation, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another implementation, to at least one, optionallyincluding more than one, B, with no A present (and optionally includingelements other than A); in yet another implementation, to at least one,optionally including more than one, A, and at least one, optionallyincluding more than one, B (and optionally including other elements);etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto.

The claims should not be read as limited to the described order orelements unless stated to that effect. It should be understood thatvarious changes in form and detail may be made by one of ordinary skillin the art without departing from the spirit and scope of the appendedclaims. All implementations that come within the spirit and scope of thefollowing claims and equivalents thereto are claimed.

We claim:
 1. A cannula assembly for an intravascular heart pump systemcomprising: a catheter; a cannula coupled to a distal end of thecatheter; and a pigtail extension coupled to a distal end of thecannula, the pigtail extension configured to position the cannula withinthe heart, the pigtail extension including: a proximal section having afirst stiffness, and a distal section having a second stiffness; whereinthe first stiffness is greater than the second stiffness; and whereinthe proximal section is positioned between the distal end of the cannulaand at least a portion of the distal section.
 2. The cannula assembly ofclaim 1, wherein the proximal section of the pigtail extension has ahardness in the range of about 60 to 100 Shore D.
 3. The cannulaassembly of claim 1, wherein the distal section of the pigtail extensionhas a hardness in the range of about 20 to 50 Shore D.
 4. The cannulaassembly of claim 1, wherein the distal section includes a curvedportion.
 5. The cannula assembly of claim 4, wherein the curved portionis curved about an axis substantially orthogonal to a central axis ofthe cannula.
 6. The cannula assembly of claim 5, wherein the curvedportion is curved by more than about 180 degrees.
 7. The cannulaassembly of claim 1, wherein the proximal section is dimensioned to havea buckling load greater than a thrust force generated by the blood pumpassembly.
 8. The cannula assembly of claim 7, wherein the distal sectionis dimensioned to have a buckling load less than a thrust forcegenerated by the blood pump assembly.
 9. The cannula assembly of claim1, wherein the proximal section of the pigtail extension has a length ofgreater than about 10 mm.
 10. The cannula assembly of claim 1, whereinthe pigtail extension is configured to detachably couple to the cannula.11. The cannula assembly of claim 1, wherein the distal section of thepigtail extension is between about 25% and 75% of a total length of thepigtail extension.
 12. The cannula assembly of claim 1, furthercomprising a pump coupled to the cannula, the cannula positioned betweenthe pump and the pigtail extension.
 13. The cannula assembly of claim 1,wherein the pump is coupled to the cannula by a pump housing componentincluding a plurality of blood exhaust apertures.
 14. The cannulaassembly of claim 1, wherein the cannula includes a blood inletmanifold.
 15. The cannula assembly of claim 1, wherein the proximalsection of the pigtail extension is composed of nylon.
 16. The cannulaassembly of claim 1, wherein the proximal section of the pigtailextension is composed of a polymer including one or more of polyurethaneand pebax.
 17. The cannula assembly of claim 1, wherein the distalsection of the pigtail extension is composed of pebax.
 18. The cannulaassembly of claim 1, wherein the distal section of the pigtail extensionis composed of polyurethane.
 19. A cannula assembly kit for anintravascular heart pump system comprising: a catheter; a cannulacoupled to a distal end of the catheter; a first pigtail extension, thefirst pigtail extension including a first proximal section having afirst stiffness and a first length, and a first distal section having asecond stiffness, the first stiffness being greater than the secondstiffness; and second pigtail extension, the second pigtail extensionincluding a second proximal section having a third stiffness and asecond length, and a second distal section having a fourth stiffness,the third stiffness being greater than the fourth stiffness; wherein thesecond length is greater than the first length; wherein the firstpigtail extension and the second pigtail extension are each configuredto detachably couple to the cannula; and wherein the first pigtailextension and the second pigtail extension are each configured toposition the cannula within the heart.
 20. A cannula assembly for anintravascular heart pump system comprising: a cannula; and a pigtailextension coupled to the cannula, the pigtail extension including: aproximal section having a first stiffness, and a distal section having asecond stiffness; wherein the first stiffness is greater than the secondstiffness; wherein the proximal section is positioned between thecannula and at least a portion of the distal section; and wherein theproximal section is dimensioned to have a buckling load greater than athrust force generated by the blood pump assembly.
 21. A cannulaassembly for an intravascular heart pump system comprising: a cannula;and a pigtail extension coupled to the cannula, the pigtail extensionincluding: a proximal section having a first stiffness, and a distalsection having a second stiffness; wherein the first stiffness isgreater than the second stiffness; wherein the proximal section ispositioned between the cannula and at least a portion of the distalsection; and wherein the distal section is dimensioned to have abuckling load less than a thrust force generated by the blood pumpassembly.